Hydrocatalytic desulphurisation of petroleum hydrocarbons



July 23, 1957 F. w. B. PORTER ETAL FEEDSTOCK FiledNQv. 1e, 1954 HEATER v- To eA/EVS.

HYDROCATALYTIC DESULPHURISATION F PETRGLEUM HYDROCARBONS Frederick William Bertram Porter and Roy Purdy Northcott, Sunbury-on-Thames, England, assignors to The British Petroleum Company Limited Application November 16, 1954, Serial No. 469,278

Claims priority, applicationfGreatiBritain November 24, 1953 '5 Claims. '(Cl. 196-28') This invention relates to the hydrocatalytic desulphurisation of petroleum hydrocarbons.

It is well known that organically combined sulphur contained in petroleum hydrocarbons vmay be vremoved by contacting the hyd-rocarbons with added hydrogen at elevated temperature and pressure -in the presence of a sulphur-resistant hydrogenation catalyst whereby the organically combined sulphur is converted to hydrogen sulphide which may readily be removed from the treated hydrocarbons. Such processes .are commonly called hydrofining processes and are usually carried out at temperatures and pressures which are optimum for the lhydrogenation reaction. Thus, pressures of the order of 1000 lb./sq. in. are employed and at such pressures :there is a considerable consumption `of. hydrogen ,the Ycost of which is an important factor in the'reconomics of the process. p

A more recent development is `the `so-called autoiining process wherein the petroleum Vhydrocarbons are contacted with a sulphur-resistant dehydrogenation-hydrogenation catalyst at a temperature and pressure such that the hydrogen required for desulphurisation is obtained ited States aten f by controlled dehydrogenation of the feedstock. Such ,a

process forms the subject of United States Patents Nos. 2,573,726 and 2,574,445-51. The autoiining process was originally operated at a fixed pressure and any yhydrogen generated in excess of that required to maintain this fixed pressure was vented from the system. It was found, however, that increased desulphurisation was obtained by recycling all the hydrogen produced during the reaction and allowing the pressure to build up to an equilibrium pressure, and this method of operation forms the subject of United States Patent No. 2,648,623.

When autoning under equilibrium p-ressure conditions, the pressure rises to a maximum within a relatively short period of 5 to 25 hours, and thereafter falls gradually as the dehydrogenating activity of the catalyst decreases. The extent of the desulphurisation follows a similar pattern. The length of the run, i. e. the hours on stream before regeneration, is .therefore governed by the rate at which the desulphurisation falls. For example, with a gas oil feedstock `of 1.3 .by weight sulphur when operating at 2.0 v./v./hr.,a bulked sulphur of 0.1% by weight is obtained over 200 hours on stream although by the end of this period the residual sulphur content is in the region of 0.3 to 0.4% by weight.

It has now been found that increased hours on stream may be obtained by maintaining the autouing equilibrium pressure by means of hydrogen added from an extraneous source, with considerably less consumption 'of hydrogen than occurs in conventional hydrotining processes.

According to the present invention, therefore, a process for the hydrocatalytic desulphurisation of petroleum hydrocarbons, comprises contacting the hydrocarbons with a sulphur-resistant dehydrogenation-hydrogenation catalyst under autoning conditions of temperature and space Velocity and recycling the hydrogen-rich gas separated l2,800,430 Patented July 23, 1957 from the treated hydrocarbons until the pressure in the reaction zone reaches equilibrium and thereafter maintainingY the equilibrium pressure prevailing at any particular time by means of hydrogen or hydrogen-rich gas added from an external source.

By operating in this manner, the fall-off of the dehydrogeuating activity of the catalyst is retarded and the hours on stream before regeneration are considerably lengthened. Although under these conditions the process is now a `nettconsumer of hydrogen, it shows considerable economic advantage in that the overall hydrogen consumption for-a given sulphur removal is reduced to l CC `only a fraction of -that obtained -when carrying -out a hydrofining operation at theconventional higher pressures.

The temperature and space velocity required for any particularfeedstock caueasily he determined by experiment but in general the following ranges vof conditions apply: r Y

Temperature n "F 'Z50-800 Space velocity v./v./hr 1-5 The equilibrium pressure obtained with any particular feedstock depends 4upon the .particular catalyst-employed, the temperature and the spacevelocity. A particularly effective catalyst consists of .the loxides of `cobalt and molybdenum incorporated with or deposited on alumina. Improved results are obtained vif the catalyst contains fluorine which is advantageously .present `in an amount between 1 and 4% by weight of the catalyst, since it has been found that'the .presence of the norine `increases the dehydrogenating` activity of the catalyst and thereby enables higher equilibrium pressures to` be built up resulting in increased desulphurisation. Methods of preparing cobalt oxide-molybdenum oxide catalyst containing fluorine are .described in .the Vspecification of United States application No. 311,429, tiled September 25, 1952.

In carrying the invention into effect, a hydrogen-rich gas may be passed to the reaction zone to maintain the maximum equilibrium pressure obtained on autoining and ifa hydrogen-rich gas is available at ay pressure below said maximum equilibrium pressure, it may be compressed to the desired pressure. In some cases, vhowever, it may be preferred .to utilise the hydrogen-rich gas without' compression, in which case it is passed to the autoning zone when the equilibrium pressure has fallen to the pressure of the hydrogen-rich gas.

The extraneous hydrogen required to maintain the equilibrium pressure may conveniently be obtained from catalytic reforming processes or may be manufactured from refinery gases by known methods.

VThe process according to ithe invention may be carried out in a plant as shown in the accompanying diagram.

The feed stock enters via line 10 and passes through a heater 11 to a Vreactor 12 in admixture with hydrogen from line 13. The products from reactor 12 pass through cooler 14 without substantial reduction of pressure toa separator 15 from which a liquid product is withdrawn via line 16, the liquid product containing dissolved therein the hydrogen sulphide formed during the reaction in reactor 12. The liquid product is passed to a stabiliser for the removal of the hydrogen sulphide and light hydrocarbon gases. The gaseous product from the separator 15, consisting largely of hydrogen, is passed via line 1'7, buffer vessel 18, compressor 19 and line 13 into admixture with the incoming feedstock. Hydrogen from an extraneous source, such as catalytic reformer exit gas, is admitted via line 20 and valve 21, the admission of such extraneous hydrogen being controlled by the pressure controller 22 to maintain the pressure in line 17 at the equilibrium pressure set up within the system.

The invention will now be described by Way of eX- Example 1 The following Table 1 compares the results obtained 4 which is approximately equal to the autofining equilibrium pressure of the feedstock under the conditions of catalyst, temperature, and space velocity, and thereafter adding hydrogen or hydrogen-rich gas from an external when operating 1n accordance with the present invention Source at a rate to mamtam ,an equlhbnum Pressure to give a product of 0.1% wt. sulphur using catalytic re- Value at a Substantlauy Constant levelformer gases containing ca. 70% mol. hydrogen to main- 2 A Pl'OCeSS aCCOfdlIlg t0 0131131 1 Whel'elll the eC1111- tain the maximum autofining equilibrium pressure, with librium pressure is maintained by means of the hydrogenthose obtained under conventional hydroiining conditions. rich gases obtained from a catalytic reforming process.

TABLE 1 Using Catalytic reformer gases to maintain the maxi- Conventional hydroflning mum auto-lining DIGSSUIS catalyst r activated oeMo oo-Mo oxides oo-Mo ondes oo-Mo oxides F amv-fated E oxides onal Y on alumina. on alumina. on alumina. Co-Mo oxides on alumina. Pressure, p. s. i. ga 320 (after hrs. on H00 500 1,000-. 0.

stream Temperature, F- R0 n 800 780 7K0 780. Space Velocity, v./v./hr 2 2 4 g 4 Y Recycle Rate, S. O. 'F./B 2,000 )(setat100p.s.i. 4,000 4,000 4,000 4,000.

Hydrogen Consumption, S. C. F./B-- 103 104 155 93 It will be seen that the hydrogen consumption for the same sulphur removal is considerably less when operating in accordance with the invention.

E Example 2 The following Table 2 compares the eiect of hours on stream on residual sulphur content when (a) autoining under equilibrium pressure conditions, and (b) maintaining4 the maximum autoiining equilibrium pressure by adding catalytic reformer gas (ca. 70% H2).

3. A process according to claim 1, which is carried out at a temperature of 750-800 F. and at a space velocity of the liquid feedstock of 1 to 5 v./v./hr.

4. A process according to claim 1, wherein said catalyst essentially consists of the oxides of cobalt and molybdenum supported on alumina and contains from 1 to 4% by'weight of iiuorine.

5. A process according to claim troleum feedstockis a gas oil.

1, wherein said pe- TABLE 2 Maintaining max. equ- Autoinlng librium pressure with cat. reformer gases Catalyst F activated Co-Mo ox- F activated Co-Mo oxides on alumina. idea on :il a. Temperature, F. 720 780. Space Velocity, v./v.lhr 2 2. Recycle rate, S. C. F./B 2,000 (set at 100 p. s. i. 2,000)(set at 100 p. s. i. Initial pressure, p. s. i. ga la' lotgi" i Hours on stream 100 150 10 50 100 150 Pressure, p. s i. ga.. 265 220 125 285 320 320 320 Residual sulphur, percent wt 0.09 0.10 0.07 0.08 0.12 0.13

It will be seen that the hours on stream for a given References Cited in the ile of this patent residual sulphur content are considerably greater in UNITED STATES PATENTS cas'gim. 2,498,559 Layng et ai Feb. 21, 195o l. A process for the hydrocatalytic desulphurisation of G0 ute "'tgee' E petroleum hydrocarbons, which comprises contacting the o er e a ug' 2,658,028 Hansel et al. Nov. 3, 1953 hydrocarbons with a sulphur-resistant dehydrogenationl 2,697,683 Engel et al. Dec. 21, 1954 hydrogenation catalyst under autoning conditions of temperature andspace velocity and recylining the hy- OTHER REFERENCES drogen-rich gas separated from the treated hydrocarbons until the pressure in the reaction zone reaches a pressure Hoog et al.: Oil & Gas Journal, vol. 52, No. 5, pages 92 and 94 to 96 (June 8, 1953).

U. S. DEPARTMENT 0F COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,800,430 July 23, 1957 Frederick William Bertram Porter et al.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Let ters Patent should read as corrected below.

Column 3, line 64, for "recylining" read recycling Signed and sealed this 25th day of March 1958,

(SEAL) Attest:

KARL H AXLINE ROBERT C. WATSON Attestng Officer Conmissioner of Patents 

1. A PROCESS FOR THE HYDROCATALYTIC DESULPHURISATION OF PETROLEUM HYDROCARBONS, WHICH COMPRISES CONTACTING THE HYDROCARBONS WITH A SULPHUR-RESISTANT DEHYDROGENATIONHYDROGENATION CATALYST UNDER AUTOFINING CONDITIONS OF TEMPERATURE AND SPACE VELOCITY AND RECYLINING THE HYDROGEN-RICH GAS SEPERATED FROM TREATED HYDROCARBONAS UNTIL THE PRESSURE IN THE REACTION ZONE REACHES A PRESSURE WHICH IS APPROXIMATELY EQUAL TO THE AUTOFINING EQUILIBRIUM PRESSURE OF THE FEEDSTOCK UNDER THE CONDITIONS OF CATALYST, TEMPERATURE, AND SPACE VELOCITY, AND THEREAFTER ADDING HYDROGEN OR HYDROGEN-RICH GAS FROM EQUAL EXTERNAL SOURCE AT A RATE TO MAINTAIN AN EQUILIBRIUM PRESSURE VALUE AT A SUBSTANTIALLY CONSTANT LEVEL. 